map! for Functor and DArray{T,N} arguments?

[dmbates]

In working on the GLM code I am converting most of the element-wise operations to

map!(f::UnaryFunctor, dest::Vector, src::Vector)

calls, which is working out very well. The stage after this will be to extend to DArray{T,1} arguments and distribute the mapping of the functor onto each chunk of the array. I'm still a little foggy on the details but I think it should be doable.

@lindahua Have you thought about this at all?

[dmbates]

cc: @JeffBezanson, @StefanKarpinski Do you think this would be straightforward to accomplish, assuming that the chunks of src and dest are aligned?

[lindahua]

I believe this is doable. Basically we can just follow what the map function does in the Base.